GreatStuff would not be good. When you spray it on an open surface any
thicker than 1/2" it forms large voids. It also does not set up very hard.
2 or 3 lb two part urethane is available from a lot of places and works well
but you have to be careful placing it so that it will not create voids or
blow out a compartment.

You might check out Fomo Handi-foam. It is a two part 2 lb spray in place
foam that comes with a disposable sprayer. It expands to full size in about
10 seconds and hardens in 2 minutes. At about $40 for a 2 cu. ft. kit it
ain't cheap but you have much better control of the placement and it
develops a very solid foam.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Donnie Gilliland" wrote in message
...
Hello all,
I'm building a 10' tunnelhull and need to add some floatation (for my own
peace of mind) in the aft section soon. I have a question concerning the
weight and ease of use of Styrofoam blocks vs. a pourable, 2 part type.
It's
a
small boat, so, I could easily cut and form blocks of Styro to fit, but
I'd
have to find some way of gluing into place, or, would I be better off
using
a pourable type? I'm convinced the Styro is much lighter but not as easy
to
make fit snuggly into place.
How about using Great Stuff from Dow, spray it in in small
layers/quantities
to allow for a complete cure before adding more?

Anyone have suggestions? What's easier? What's more worth it? Any pourable
Mfgr's suggestions?
I'm a newby to boat construction but NOT to woodworking.

Thanks in advance
Don